The present invention generally relates to an image forming apparatus and more particularly to a method of discharging waste toner from the image forming apparatus.
For printers and image forming apparatus, electrophotography has come into common use for its high printing speed and reliable storage of images.
In an electrophotographic apparatus, a charging roller rotates in contact with a photoconductive drum to negatively charge the surface of the photoconductive drum. Then, light generated from a laser or an LED array illuminates the charged surface of the photoconductive drum in accordance with print data to selectively dissipate the charges, thereby forming an electrostatic latent image on the surface of the photoconductive drum. A developing roller rotates in contact with the photoconductive drum, thereby depositing negatively charged toner particles to the electrostatic latent image to form a visible toner image. A print medium is advanced with its front side in contact with the rotating photoconductive drum and its back side charged positively, so that the toner image is transferred onto the front side of the print medium by the Coulomb force of the positively charged back side.
The surface of toner particles is covered with surface additives such as an abrasive and silica. When the toner particles are rubbed between a toner supplying roller and a developing roller, the physical forces applied to the toner particles damage the particle surfaces to remove the surface additives.
Heat and force resulting from friction cause the toner particles to break and/or stick to other particles into agglomerates. Such deteriorated toner particles accumulate in a developing unit and cause non-uniform image density and poor reproducibility of dots.
For example, a large number of pages are sometimes printed with a low print duty, i.e., the ratio of a total area of a print medium occupied by toner to a total area of the print medium not occupied by toner is large. Low print duty implies that the toner particles stay for a longer time within an ID (image drum) unit and is therefore subject to physical damages due to friction. Silica is one of the surface additives and adds fluidity to the toner particles so that toner can be agitated efficiently and toner images can be transferred efficiently. Abrasives prevent xe2x80x9cfilmingxe2x80x9d of the toner from being formed on a developing blade. Toner particles from which surface additives have come off are apt to stick together into agglomerates and are deposited on the developing blade.
The developing blade is provided in order to make a thin layer of toner on the surface of the developing roller. If agglomerates of toner are formed on the developing blade, a uniform thin layer of toner cannot be formed on the developing roller so that no toner is deposited to an image area on the photoconductive drum that corresponds to the agglomerates of toner.
If images are printed with a high print duty (i.e., a total area occupied by the toner to a total area not occupied by the toner is low) after images are printed with a low print duty, image areas that correspond to the toner agglomerates are not properly developed. This results in white lines on the printed images.
An object of the invention is to provide an image forming apparatus and a method of controlling the image forming apparatus in such a way that even when printing is performed with a low print duty after printing with a high print duty, the print quality is maintained.
Another object of the invention is to provide an image forming apparatus and a method of controlling the image forming apparatus by employing firmware instead of improving the toner, surface additives to the toner, or toner agitating mechanisms.
An image forming apparatus includes an electrophotographic image forming section and a controller. The electrophotographic image forming section forms a toner image on a print medium. The controller causes the image forming section to form the toner image of a pattern image on the print medium when a cumulative operation reaches a predetermined value.
The cumulative operation is one of a number of print jobs, a number of printed pages, and a number of rotations of an image drum.
The cumulative operation is a number of printed pages having a print duty less than a predetermined value.
The pattern image is at least one of a number of pattern images aligned in an advance direction, the number of pattern images being increased in accordance with a print duty.
The controller divides a print region of the print medium into a plurality of sub-divided areas that are aligned in a traverse direction, and calculates a cumulative print duty in each one of the plurality of sub-divided areas and causes the image forming section to print the pattern image in a sub-divided area in which the cumulative print duty is less than a predetermined value.
The controller causes the image forming section to print an activity report at predetermined time intervals and the pattern image together with the activity report on the print medium.
The image forming section includes a photoconductive drum, a developing unit that supplies toner to the photoconductive drum to form the toner image, a transfer unit that transfers the toner image from the photoconductive drum to the print medium, and a cleaning unit that collects waste toner from the photoconductive drum. When the waste toner is collected from the image forming section, the transfer unit receives such a voltage that no transfer of toner occurs between the photoconductive drum and the transfer unit so that the waste toner is collected through the cleaning unit.
The image forming section further includes
a charging unit that uniformly charges a surface of the photoconductive drum,
an exposing unit that illuminates the charged surface of the photoconductive drum to form an electrostatic latent image of a predetermined pattern image in accordance with a difference between a predetermined amount of printing and a number of actually printed dots, and a developing unit that supplies the toner to the electrostatic latent image.
The controller divides a print region of the print medium into three areas that are aligned in a traverse direction, an area between two areas having a smaller print duty than the two areas.
A method of controlling an image forming apparatus includes the steps of:
causing an electrophotographic image forming section to form a toner image on a print medium; and
causing the image forming section to form the toner image of a pattern image on the print medium when a cumulative operation reaches a predetermined value.
In the method of controlling an image forming apparatus, the cumulative operation is one of the number of print jobs, the number of printed pages, and the number of rotations of an image drum.
In the method of controlling an image forming apparatus, the cumulative operation is the number of printed pages having a print duty less than a predetermined value.
In the method of controlling an image forming apparatus, the pattern image is at least one of the number of pattern images aligned in an advance direction, the number of pattern images being increased in accordance with a print duty.
The method of controlling an image forming apparatus further includes the steps of:
dividing a print region of the print medium into a plurality of sub-divided areas that are aligned in an advance direction; and
calculating a cumulative print duty in each one of the plurality of sub-divided areas and causes the image forming section to print the pattern image in a sub-divided area in which the cumulative print duty is less than a predetermined value.
The method of controlling an image forming apparatus, further includes the step of:
causing the image forming section to print an activity report at predetermined time intervals and the pattern image together with the activity report on the print medium.
In the method of controlling an image forming apparatus, the image forming section includes a photoconductive drum, a developing unit that supplies toner to the photoconductive drum to form the toner image, a transfer unit that transfers the toner image from the photoconductive drum to the print medium, and a cleaning unit that collects waste toner from the photoconductive drum. The method further includes applying such a voltage that no transfer of toner occurs between the photoconductive drum and the transfer unit so that the waste toner, is collected through the cleaning unit, the voltage being applied when the waste toner is collected from the image forming section.
In the method of controlling an image forming apparatus, the image forming section further includes:
a charging unit that uniformly charges a surface of the photoconductive drum;
an exposing unit that illuminates the charged surface of the photoconductive drum to form an electrostatic latent image of a predetermined pattern image in accordance with a difference between a reference print duty and an actual print duty; and
a developing unit that supplies to the electrostatic latent image;
wherein the method includes causing the developing unit to supply the toner to the electrostatic latent image.
The method of controlling an image forming apparatus further includes dividing a print region of the print medium into three areas that are aligned in a traverse direction, an area between two areas having a smaller print duty than the two areas.
A further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.